Anion-Exchange Membrane Water Electrolyzers for Green Hydrogen Generation: Advancement and Challenges for Industrial Application

Hydrogen is emerging as a strong contender for a feasible future energy carrier in the clean energy race, due to its high energy density and clean burning nature. However, to account for the environmental and energy challenges, its production must be sustainable and cost-efficient. Currently, hydrogen is generated from various feedstocks such as ammonia, methane, natural gas, biomass, smaller organic molecules, and water. These feedstocks undergo different catalytic processes, including catalytic decomposition, electrolysis, steam reforming, pyrolysis, gasification, and photoassisted methods such as photoelectrochemical, biophotolysis, and photocatalysis, etc. Among all, the research on water electrolysis has garnered much attention because of their carbon free green hydrogen production with the use of water electrolyzers (WEs). On the basis of recent reports from the International Renewable Energy Agency (IREA), the major types of water electrolyzers used in the industry are alkaline water electrolyzers (AWE), proton-exchange membrane water electrolyzers (PEMWEs), and anion-exchange membrane water electrolyzer (AEMWE). Among them, AWEs and PEMWEs have their inherent drawbacks which need attention. AEMWEs can be considered as a promising alternative by integrating the advantages of both AWEs and PEMWEs into one device. In this review, we have focused on the core ideas of AEMWEs, where the recent scientific and engineering breakthroughs are highlighted. It points out the importance of eliminating the gap between electrodes (i.e., zero gap concept) and identifies areas that need further development to push AEMWE technology forward. AEMWEs offer advantages such as higher operating current densities and pressures, comparable Faradaic efficiencies (>90%), and the utilization of nonprecious metal catalysts along with pure water feed. Along with all these, we have also focused on the advancements and deterioration of AEMs. Additionally, it provides a concise overview of AEMWE membrane performance and offers a detailed examination of developments in electrolyte feeding and the utilization of nonprecious group metal (non-PGM) electrocatalysts.